Fluid type seal



SeptD 25, 1945. E DAYTON 2,385,406

FLUID TYPE SEAL Filed Sept. 2, 1941 2 Flan.

ERMES-T L. onion FIGA. me

PatentedSept. 25,1945

FLUID TYPE SEAL Ernest L. Dayton, Detroit, Mich. i Application September 2, 1941, Serial No. 409,303v

` (ci. sos-s3) Claims.

This invention relates generally to iiuid seals of the type employed in iiuid pressure systems and refers more particularly to an improved liquid seal for preventing the escape of a hydraulic iiuid medium in one direction past a piston.

It has been proposed to prevent the escape of J fluid past a piston in a hydraulic system by providing a rubber cup-shaped seal having a base portion seated against the lpressure end of the piston and having an annular flange frictionally engaging the adjacent wall of the cylinder. It

cup-shaped sealing eter than the internal diameter of the cylinder and in view of the fact that the annular lip on.

has been found that in use the base portion of the seal vhas a tendency to extrude into the limited operating clearance provided around the piston and this, of course, caused undue wear of the seal.

It is one of the principal objects of this invention to overcome the above objection by providing a seal having a Vcup-shaped member of resilient material and having a self-sizing member of relatively good wearing material surrounding the base of the seal to protect the latter.

Another object of this invention resides in the provision of a double seal having axially spaced annular sealing lips, one being formed on a ductile material andY theother being formed of a resilient material, such as rubber or a substitute for rubber. l

Another object of the present invention resides in the provision of a double seal having a cupshaped member provided with an annular sealing lip of ductile material at the free edge thereof and havingl a cup-shaped member of resilient material provided with a base portion seated with- ,Y in the cup aforesaid and further provided with an annular sealing lip spaced-axially from the ductile sealing lip, previously referred to.

Still another object of this invention consists in providing a lseal of the type previously set .forth lwherein the outside diameter ofthe annular flange on the outer cup is slightly less than the inside diameter of .the cylinder within which the seal is adapted to operate andwherein the diameter of the 11p of nexible material. on the inside l cup is slightly greater than the internal diameter of the cylinder so as to have a uniform wiping engagement with thecylinder wall upon movement of the seal axially of the cylinder.` The arrangement is such that-the lip on the inside cup initially forms an eilective seal with the cylinder wall and the ductile lip on the outer cup responds to pressure rise in the cylinder to expand outwardly into engagement with the cylinder wall so that under working pressures, a compound seal results. Also, inasmuch as the lip on the inner the outer cup member is of ductile material, it follows that an effective seal is maintained regard- I less of wear of the cylinder wall.

A further advantageous feature of the present invention resides in the provision of a compound seal wherein the ductile material from which the lip is formed has no denite elastic limit with the -result that therev is no tendency for the lip to move inwardly or away from the cylinder wall during operation and,oat the same time, permits expansion of the lip under pressures so light that the resistance` offered to sliding movement of the seal relative to the cylinder wall is negligible.

The foregoing, as well as other objects, will be made more apparent as this description proceeds,

especially when considered in connection with the accompanying' drawing, wherein: Figure l is a. semi-diagrammatic sectional view of a wheel cylinder forming a part of a hydraulic brake system and embodying my invention;

Figure 2 is a semi-diagrammatic sectional view of a master cylinder having a seal constructed in accordance with this invention;

Figure 3 is a cross sectional view taken substantially on theplane indicated by the line 3,-3' of Figure 2:

'Figure 4 is a enlarged sectional view illustrating my improved compound seal construction;

Figure 5 is a cross sectional view through a slightly modified form of seal construction.

For the purpose of illustrating thisinvention, I have shown my improved compound seal as used in connection with a hydraulic brake system, al-

' though it will be apparent as this description proceeds that the seal is not limited to this particular application and may` be advantageously used in practically all cases wherea sliding seal is desired. In detail, I have illustrated in Figures 1 and 2 a hydraulic brake system lhaving a compressor Ill` and-a brake'shoe actuating device Il operatively connected to the compressor.

The compressor lli comprises a piston i2 reciprocablyvmounted in a cylinder Iscommimieating with a reservoir I4 adapted to contain al suitable vhydraulic iiuid medium.l In the present instance, the reservoir communicates with the portion of the cylinder at the low pressure side of the piston by means of a port I5 and the fluid in the portion of-the cylinder at the lowl pressure side of the piston is admitted to the portion of the cylinder at the high pressure side of the piston through the medium of passages II.

member is of greater diam- The piston I2 is normally urged to its retracted position shown in Figure 2 by means of a spring il' and is movable against the action of the spring toward the high pressure' end of the cylinder by any one of the accepted types of control devices (not shown). It will sumce to point out that movement of the piston l2 in a direction against the action of the spring lli exerts y a pressure on the duid medium in the cylinder at the high pressure end of the piston and forces this fluid medium through a suitable delivery conduit, designated in Figure 2 by the reference character assesses .2@ is of less diameter than the internal diameter vel? the cylinder it. On the other hand, the annula'r sealing lip portion 25 on the inner cupshaped member 2l is of greater diameter than the inside diameter of the cylinder I3. As a result, when the seal isr initially inserted in the cylinder, the annular lip 25 on the inner memface 22 of the annular flange on the cup-shaped member is tapered outwardly at the free end of the member toiorm a sealing lip 28. The lip 2S on the free edge portion of the annular ange I of the cup-shaped member is formed of a ductile material so as to permit the same to be readily expanded into engagement with the cylinder wall. In the interests of simplicity, the entire cupshaped member 2u lis shown herein as being formed of a ductile material although in most ap-A plications, it would be sumcient to fashion only the annular' ilange or lip. portion of the cupshaped member from such a material.

The inner cup-shaped member 2i is formed of a resilient material, such as rubber or a substitute for rubber and the dimension of the mem- Yber 2| is such as to permit the same to be nested lwithin the uter member in the manner shown in Figure 4. The annular ange 24 of the inner cup-shaped member 2l extends beyond the sealing lip 23 and the inner surface of this flange is also tapered outwardly at the free end of the cup-shaped member 2l to form s sealing lip 25. It follows from the above that the sealing lip 25 lbe obtained by forming the onthe inner cup-shaped member 2| is spaced axially from the lip 23 on the outer cup-shaped member 20 and cooperates with the lip 23 to form` a double seal.

The double seal I9, previously described, is assembled on the high pressure end of the piston I2 with the base 26 of the outer cup-shaped member bearing against the piston, and with the base 21 of the inner cup-shaped member 2| forming an abutment for one end of the spring I1. As v a result, the spring I1 yleldably holds the two cup-shaped members in assembled relationship against the high pressure end of the piston. In the specific application ofthe seal I9 shown in Figure 2, provision must be made for' the hy.- draulic Auld medium to ilow from the low pressure side of the piston to the high pressure side of the latter around 4the seal. 'Ihis may be ac'- complished by forming an annular groove 2B in the outer surface of the base 26 of the member 20 in a manner that this groove registers with the adjacent ends of thepassages IB. The annular groove 2B, in turn,lcommunicates with the interior of, the cup-shaped member 20 and the underside ofrtheeresilient member through the medium ofcircumferentially spaced passages 29 and, since the inner cup-shaped member 2| is merely yieldebly I ield in bled relationship ber 2l irictionally engages the wall or the cylinder to formylhat may` be termed a static seal. However, as soon as pressure is applied to the annular snge portions of the two cupshaped members, the lip ZS or ductile material von the outer cup-shaped member expands into vregardless of wear or slight inaccuracies in the cylinder wall. It may also be pointed out that the material from which the cup-shaped member 20 is formed is so selected that it has no deilnite elastic limit and, consequently, will not tend to move radially .inwardly once it is urged outwardly by the operating pressure. It has been found that particularly satisfactory results may ductile sealing member 20 of a metal alloy having tin or cadmium as the principal base metal. However, the invention should not be limited to the use of ductile metals because certain types of plastics have 'ductile characteristics and may be employed to form the seal 20.

Upon reference to Figure 1, it will be noted that the actuating device II for the brake friction means comprises a cylinder 30 having pistons II reciprocably mounted therein between the actuator ends 32 of the brake friction means, and respectively engageable with the latter ends of the brake friction means. The portion of the cylinder between the adjacent ends of the pistons communicates with the delivery conduit I8 to re`ceive iluid under pressure from the high pressure end of the compressor cylinder I3 when the piston I2 is moved against the action of the spring J1. In accordance with conventional practice, the duid under pressure admitted to the cylinder 30 between the pistons 3i moves the latter outwardly and expands the brake friction means into enge-gement with the brake drum (not shown).

With the above construction, it is also desirable to prevent the escape of fluid under pres sure past the pistons 3| and this is accomplished Aby a -pair ofcompound seals 33 (Fig. 1) respectively held in assembled relation with lthe adiacent endspof the pistons 3l by means oi the spring 8l. The seals` are identical in construction to' the seal I8 previously described, with the exception that the base portions is of the outer cup-shaped member 36 are impexforate since it is not necessary to provide for the trans fer of fluid past the seal.

the cylinder.

of the piston e flange of ductile metal alloy having as the prin- Referring now to the seal shown in Figure 5, lt willbe noted that'this seal diners from the previously described' constructlons'in' that a-third relatively shallow cup-shaped member, is provided having a iiange 31a for recelvingthe base portion 2i' of the cup-sha The cup-shaped member of steel or of a metal having a hardnessz'substantially greater than the ductilematerial from which the seal 2l' is fashioned. This-upstand-- ing ilange. construction is where the entire cup-shaped member 2n' 'is fashioned from a ductile material since Vit prevents spreading or creeping ci' the base portion 20 of the cup-shaped 'member' 2l' high pressures. A

It will be noted that in each ofthe embodiments of the invention, the base of the inner cupshaped sealing member isprotected bythe base portion of the outer cup-shaped sealing member. This arrangement is particularly advantageous in cases where the inner member is formed of rubber or a substitute for rubber in that it e'llmlsealing member Il'.

l1 is preferably 'formed v -under abnormally assumes lip of greater ameter of the cylinder for the cylinder wall.

maniere: than the internal di; frictionally engaging 4. A seal for use in iluid pressure systems having a relatively reciprocable cylinder and piston;

said seal comprising a cup-shaped member formed of-ductile metal having a base portion particularly desirable positioned at the pressure end of the piston and having an annular ilange terminating in an annular lip engageable with the cylinder wall, and

a second cup-shaped member formed` of rubber material nested in the nrst named cup-shaped lmember and having'an annular ilange projectpositioned nates the danger o! the base portion of the inner member extruding around the piston and causing undue wear of the seal. j

What I claim as my invention is:

1. A seal for use in fluid pressure systems havl ing a relatively' reciprocable cylinder and piston. said seal comprising a member positioned -at the pressure end oi thepiston and having an annular flange provided with an' endlessannular lipo'f Aductile material engageable with. the -cylinder wall, and a second member seated within-the nrst memberand having an annular 'nange o1' resilient material projecting beyond the annular lip of the iirst member, the annular .flange on said second member also terminating in an annular lip engageable with the cylinder wall in spaced relation -to the first named annular lip axially of 2. A seal for use in fluid pressure systems having a relatively reciprocable cylinder andpiston,

said seal comprising a cup-shaped member hav' ing a base portion positioned at the pressure end and having an endless annular jecting beyond the annular ange of the `ilrs't named cup-shaped member and also'terminating in an annular sealing lip engageable' with the f ving a relatively reciprocable cylinder and piston, Asaid seal comprising a cup-shaped member of cylinderv wall.

3. A seal for use in fluid pressure systems having va relatively reciprocable 'cylinder and piston,

said seal comprising soup-shaped member. `having abase portion positioned at the pressure end said ange adapted to expand under the action ing beyond the annular lip on the ilrst named liange, the annular flange on the second member also terminating in an annular sealing lip frictionally engageable. 'with the cylinder wall in spaced relation to the ilrst named lip axially of the cylinder.

5. A seal for use in iluid pressure systems having s relatively reciprocable cylinder and piston.

said seal comprising a member having a portion at the pressure end' of the piston and having an endless annular ilange of ductile metal alloy having as the principal base metal, a metal ofthe class consisting of tin and cadmium, the free edgeportion of said annular ilange being tapered radially outwardly -to form an' annular sealing lip engageable with the cylinder wall, and a second member seated against 'the member aforesaid within the latter and having an annular-rlange of resilient material projecting beyond the iirst named ilange, the tree edge por- A tion ot the .second named annular ilange being tapered radially outwardly to form a second annularsealing lip engageable vwith the cylinder wall axially beyond the first named lip.

6. A seal for use in iluid pressure systems having a relatively reciprocable cylinder and piston, said seal comprising a cup-shaped member of ductile metal having a base portion positioned at the pressure end of the piston and having an annular ange terminating in an annular lip engageable 4with the cylinder wall, a second cupshaped member nested in the nrstenamed cupshaped member, and having an annular ange ot `.resilient material extending beyond the. lip

1 on said rst named cup-shaped member, said second annular iiange also terminating in an annular lip frictionally engageable with the cylindex' wall axially beyond the first mentioned lip,

and means surrounding the base portion 'or the iirst named cup-shaped member and eiective to of fluid pressure into sealing engagement'with the cylinder wall, and a second cup-shaped member having a base portion extending into the nrst cup-shaped member and seated against the base portion of the latter, said Lsecond cup-shaped member having an annular ange of resilient material projecting beyond the nrst Anamed annular ilange and terminating in an annular sealholdy the ductile metal in the base portion ofthe first mentioned cup-shaped member from creeping outwardly under the action of iluid pressure.

"7. A seal for use in fluid pressure systems havductile metal having a base portion positioned -at the pressure end ofthe piston andl having Y-lip frictionally engageable with the cylinder wall axially'beyond the vfirst mentioned lip, and a third cup-shaped member of a relatively hard metal having a base interposed between the base or thev ilrst cup-shaped-member and the pressure end of the pistonand having an annular flange embracing a portion oi' the annular ilange on the rst mentioned cup-shaped member to prevent creeping of the duotile motel forming the bese portion of the rst named cup-shaped member.

8. A seel for use in uid pressure systems hsving a, relatively reciprocable cylinder and piston,

said seal comprising e cup-shaped seal of resilient materiel positioned with the base portion adjacent the pressure end o. the piston, end a; member having en endless annuler portion of ductile metal eiloy having as the primcipel bese metal, e. motel of the class consisting orA tin und cadmium surrounding the bose portion of the seal end slidably engaging the cylinder well.

9. A seul for use in fluid pressure systems having e. relatively reciprocnble cylinder and piston,

said seei comprising a, oup-sheped member heving e' bese portion positioned et the pressure end der pressure owing through said port and passage, to permit the fluid to escape to the pressure sideof the piston, and a.l sealing lip on the free end of the second cup-shaped member positioned beyond the lip on the rst member and engsgeable with the cylinder well.

l0. A .seal for use in fluid pressure systems having e, relatively reciprocable cylinder and piston, said seal comprising three cup-shaped members nested together and positioned. et the pressure endof the piston with the snges extending outwardly from the piston in the `general direction of the exis of the letter, the intermediete member being formed of ductile metal end having the extremity of the enge thereof engsgeeble with the cylinder well, the inner member being formed or e resilient materiel ond having en annular lip portion on the extremity or" the enge thereof projecting beyond the enge on the ductile member for enneigement with the cylinder well, and the outer cup-shaped member being formed of e, motorini which is more rigid than the ductile metal of the intermediate A member and is provided with a relatively short enge which embraces the bese portion of the intermediate member to prevent spreading of the letter.

ERNEST L. DAYTON. 

